Spark gap



F. L. JONES Sept. 21, 1948.

" SPARK GAP Filed May 9, 1945 I FIG. 41 FIG. 6

FIG.

Inventor Patented Sept. 21, 1948 UNI-TED STATES FEATENT QFFICE.

SPARK GAP I TIT-rank" Llewellyn Jones, Mil lbankpLo ndon, England,as'signor to Minister of Supply, in. His

Majesty's Government of the United Kingdom of Great Britain-and NorthernIreland, London,

England I Application May-9,, 1945, Serial No. 592,843

In GreatBritain Mayllli, 19M

This invention relates to improvements. in

spark gaps operating. inan. enclosed envelope of the type whi'chisrequi'redt'o operate on pulses of el'ectromotive'force of alternatepolarity for pro-,v

electrodes at high sparking rates (in exces of about 250: sparksrpersecond).

In my prior specification Serial 585,165, filed March 27, 1945, sparkgapsa-re-described in which the electrodes are arranged in asealedenvelope filled with an inert gas witha substantially uniformelectric" field created betweenthe electrodes 01" in whichapairof' suchgaps-are arranged in parallel electric circuits to distribute the'sparking between the twopairs'ot'electrodes in order that the rate ofsparking in each gap may be reduced.

'It'h'as'been found, however, that with two similar gaps arranged inparallel the sparking is not evenly distributed between the two and thatoverloading of one gap is liable to occur and that after the failure, e.g. increase of impulse ratio of one gap due to overloading, theremaining gap being forced to carry the full sparking rate may alsofail.

Further in such spark gaps it is necessary to form the electrodes inorder to provide a substantially steady or constant breakdown potentialof the gap before sealing ofi the envelope which entails operating thegap for a considerable period in air.

The object of the present invention is to obtain a polarity sensitivespark gap, 1. e., one which has a lower statistical lag when anelectrode or a particular portion of the electrode is the cathode thanwhen that electrode or portion is the anode, whereby the rate ofsparking across the gap or across the particular portion of the gap whenoperating on pulses of alternating electromotive force may be reduced toone half by a positive control of the sparking across the gap.

The invention comprises a spark gap so conditioned or disposed that twopaths for electrical impulses are provided, one path sensitive to elec-Claim's'. (01. 250-27.5)

tri'cal impulses of one polarity and the other path sensitive toelectrical impulses of the opposite polarity, the sparkingv potenial ofboth paths being substantially equal.

The invenion will be described with reference to the accompanyingdrawings which showalternative arrangements of the electrodes.

Fig. 1 shows a gap employing two pairs of electrodes arranged in thesame envelope.

Fig. 2I'shows two pairs of electrodes mounted in separate envelopes andelectrically connected in parallel.

Fig. 3 shows a pair of composite electrodes arranged in an envelope.

' Figs. land 5 show face views (enlarged) of the two electrodes shown inFig. 3.

Figs.. 6 and 7 are sections on line 6-6, Fig. i, andline l-LFlg. 5,respectively.

In one form of the invention two spark gaps l and 2 arranged in anenvelope 3 are electrically connected in parallel, one electrode 4 ofeach pair being, for example, of tungsten and the other electrode. 5 ofeach pair having an oxide sintered.

on to the; tungsten, for example, titanium oxide.

(T102), aluminium oxide (A1203), or magnesium oxide (Mg',O).,. which ithasbeen found will provide=polarity sensitive gaps, i. e., thestatistical lag of the gap is less when the oxided electrode is thecathode. Thus with the gaps arranged in parallel as shown in Figs. 1 and2, when one pair of parallel electrodes 4 and 5 of gaps l and 2,respectively, are cathodes, gap 2 will operate and gap I will beinoperative since the statistical lag of gap 2 with electrode 5 ascathode is less than that of gap I. Similarly on the next pulse of0pposite polarity the statistical lag of gap I will be the lesser as itselectrode 5 is then the cathode and gap '2 will be inoperative.

The electrodes, instead of being in a single envelope 3 as shown in Fig.1, may be arranged in separate envelopes 6 as shown in Fig. 2, the twopair of electrodes being electrically connected in parallel outside theenvelope.

In the arrangement shown in Figs. 3-6 a composite pair of electrodes areemployed having two concentric portions, the outer portion 1 of oneelectrode being of tungsten with an oxided portion 8 inset thereinwhilst the second electrode is formed with a central portion 9 oftungsten and an outer concentric oxided portion In,

Instead of providing the oxided electrode by sintering the oxides withthe tungsten, they may be embedded in or produced on the tungsten in anyother suitable manner such as by forming 3 the electrode as described inmy earlier specification Serial No. 585,165.

In all cases the object is to reduce the statistical lag for one path onnegative polarity and to maintain a high statistical lag for the otherpath on the same polarity and vice versa.

The envelopes are preferably filled with a gas,

for example, commercially obtainable nitrogen as it has been found thatany impurities therein do not adversely afiect the operation of the gapsand are advantageous for are quenching.

By employing two pairs of gaps in parallel, i. e. two gaps in parallelsensitive to pulses of electromotive force of positive polarity and twogaps in parallel sensitive to pulses of electromotive force of negativepolarity, the sparking rate in each pair of polarity sensitive gaps maybe still further reduced but no positive control will be obtained asbetween the two gaps operating on the same polarity.

The electrodes have been described as being composed of tungsten as thismetal has been found to have advantages, but the invention is notlimited to the use of this particular metal.

I claim:

1. A spark gap of the type referred to for operation on pulses ofelectromotive force of alter" nate polarity comprising two plateelectrodes disposed parallel to one another in an envelope containinggas, said electrodes providing two polarity sensitive conducting pathsfor the electrical impulses between said two parallel plate electrodes,one path being sensitive to electrical impulses of one polarity and theother path sensitive to electrical impulses of the opposite polarity,the sparking potential of both paths being substantially equal.

2. A spark gap of the type referred to for operation on pulses ofelectromotive force of alternate polarity comprising two plateelectrodes dispose-d parallel to one another in an envelope containinggas, said electrodes providing a polarity sensitive conducting paththrough one portion of the electrodes sensitive to electrical impulsesof one polarity and a second polarity sensitive conducting path througha further portion of said electrodes sensitive to electrical impulses ofthe opposite polarity, the sparking potential of both paths beingsubstantially equal.

3. A spark gap of the type referred to for operation on pulses ofelectromotive force of alternate polarity comprising two pairs of plateelectrodes electrically connected in parallel, each plate electrodebeing disposed parallel to the other plate electrode of the pair in anenvelope containing gas, one pair sensitive to electrical impulses ofone polarity and the other pair sensitive to electrical impulses of theopposite polarity, the sparking potential of both pairs beingsubstantially equal.

4. A spark gap of the type referred to for operation on pulses ofelectromotive force of alternate polarity comprising two pairs of plateelectrodes electrically connected in parallel, each plate electrodebeing disposed parallel to the other plate electrode of the pair, onepair sensitive to electrical impulses of one polarity and the other pairsensitive to electrical impulses of the opposite polarity, the sparkingpotential of both pairs being substantially equal, and an envelopecontaining an inert, gas by which the two pairs of electrodes areenclosed.

5. A spark gap of the type referred tofor operation on pulses ofelectromotive force of alternate polarity in which a conducting path oflow time of lag of spark under the applied electromotive force isprovided by a cathode electrode of tungsten sintered with an oxide and atungsten anode and a conducting path of higher time of lag of sparkunder the applied electromotive force is provided by a cathode electrodeof tungsten and an anode of tungsten sintered with oxide.

FRANK LLEWELLYN JONES.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Great Britain Apr. 25, 1929

